SU1320254A1 - Inoculating mixture for malleable cast iron - Google Patents

Abstract

The invention relates to the metallurgy of alloys, namely to modifiers of liquid iron, and can be used in the production of castings from ductile iron. The aim of the invention is to improve the mechanical properties of cast iron. The proposed modifying mixture contains, in wt.%: Aluminum 4.7-5.7; boron 0.5-0.55; bismuth 0.7-0.75; copper oxide 93.0- 94.1. The use of the proposed modifying mixture makes it possible for a cast iron to have a tensile strength of 42-45.5 kg / mm, a hardness of 131-163 HB and reduce the duration of heat treatment from 34 to 19 hours. Table 3. i (L

Description

The invention relates to the metallurgy of alloys, namely to modifiers of molten iron, and can be used in the production of castings from ductile iron,

The aim of the invention is to increase the mechanical-properties and reduce the duration of heat treatment of the cast iron.

The proposed modifying mixture contains aluminum, boron, bismuth and copper oxide in the following ratio of components, mA s,%:

Aluminum4.7-5.7

Bor0,5-0,55

Bismuth 0.7 - 0.75

Copper Dross 93.0-94.1

The chemical composition of the mixtures is presented in table. one..

Example: Each modifying mixture was prepared separately by mixing the components. With the release of liquid iron (composition, wt.%: C 2.4 Si 1.1; MP 0.4; Cg 0.06; S 0.06; P 0.07), the cupola –– electric arc produced oven, modifying mixture at 1500 C consistently introduced into six buckets. Then the modified cast iron was cast into molds and at the same time prototypes were cast to study the mechanical properties.

The presence of copper scale in the modifying mixture above 94.1 wt.% Results in the appearance of gray iron in the structure, i.e. plate granite, which leads to a decrease in mechanical properties.

The content of copper scale below 93% in the proposed modifying mixture leads to a decrease in the rate of graphitization, to the deterioration of the shape of graphite, which leads to a deterioration in strength and hardness,

The decrease in the composition of the modifier of the upper input limit of bismuth from 0.02 to 0.002% by weight of the liquid metal). It is possible, since oxygen introduced with copper scale will prevent the release of free graphite, i.e., perform the same role as bismuth due to the stabilization of the liquid melt. In addition, it is possible to reduce the consumption of alumi- num graphitizers and boron due to the introduction of copper into the metal, which enters the cast iron from copper scale, introduced into the modifier.

five

five

The use of a copper core in the composition of pre-cast iron is related to the fact that it consists of a set of oxides (oxide, nitrous oxide), that is, e. contains nons with charges of +2 and +4, for example, CuO are two copper ions, which deepens, strengthens and accelerates the process of graphitization. An ion with a higher charge has greater mobility and activity. The process of interaction of ions at high temperatures is the main process of increasing the number of carbon nests in the annealing of white cast iron, modified with the proposed MJsiM modifier and transformed into ductile iron. This has a positive effect on the reduction in the duration of heat treatment and the increase in mechanical properties. The presence in the modifying mixture of less than 93% of copper scale (composition 5) leads to a decrease in the graphitization rate of cast iron in the solid state and, accordingly, to an increase in the duration of annealing.

The presence in the modifying mixture of more than 94.1% of copper scale (composition 4) leads to a relative decrease in the amount of the carbide stabilizing element (bismuth) and, accordingly, to the appearance of gray iron in the structure, i.e. deterioration of the shape of graphite and release of free lamellar graphite during crystallization of liquid iron, which is unacceptable and leads to marriage, and, moreover, stabilization of perlite, which significantly increases the duration of the second stage of annealing and, accordingly, of the whole cycle.

The modifying mixture was introduced into the iron in the amount of 0.2-0526 by weight of the liquid iron, the modifying mixture is known in the amount of 0, 0.076 by mass of the liquid metal.

The optimal is the addition of a modifying mixture (providing an introduction to the iron, wt.%: Aluminum 0.01-0.015; boron 0.001-0.0015; bismuth 0.0015-0.002; copper oxide 0.2-0.25, and in the known a mixture of wt%: aluminum 0.01-0.05; boron 0.001-0.006 and bismuth 0.001-0.02.

The cast samples, modified by the proposed mixture, were subjected to heat treatment according to the mode: heating to 960 C (8 h), holding at this temperature for 5 h, intermediate

cooling to {h), holding at this temperature for 5 hours and cooling in air. Samples modified with a known mixture were subjected to heat treatment according to the following conditions: heating to 960 C (8 h), holding at this temperature for 12 h, intermediate cooling to 740 ° C for 1 h), holding at this temperature for 13 h and cooling on air,

The graphitization of white cast irons containing the addition of copper in them has a peculiarity in that: in the presence of bismuth in the iron, copper forms with it a low-melting eutectic located on the grain boundaries.

This eutectic, the constituent composition of the mother liquor, during crystallization is of decisive importance in accelerating the process of graphitization. This is especially important during the annealing of white cast iron on ductile, where it, being an active medium, promotes the formation of smaller and more compact carbon emissions of annealing and is usually located along the grain boundaries of ferrite, which contributes to an increase in the mechanical properties of cast iron.

The process of carbon coagulation of annealing is also associated with the function of this mother liquor, which, solidified last, tends to its maximum in the stock of internal energy, thereby compressing the more crushed ferrite grains and creating more favorable graphitization conditions in elemental volumes of cementite containing submicroscopic spelled graphite.

The presence of the mother liquor, which contains a low-melting copper eutectic eutectic, plays the role of the active medium in the formation of the scientific research institute of surface-active films that promote the coagulation of carbon annealing. In addition, at high temperatures, copper oxides decompose and at the same time copper ions can interact with iron ions, located both near the interface of the grains and in the grains themselves due to the dissolution of copper in iron and substitution reactions, creating further sources of carbon annealing.

five

0

five

50

 cast iron,

This process,: with the interaction of ions at high temperatures, is the main process of increasing the carbon nests of annealing in white iron, turned into ductile iron, observed in the study of white iron, modified by the proposed modifier. Thus, the heat treatment process is reduced from 34 to 19 hours,

The mechanical characteristics of the obtained castings (prototypes) are given in Table 2 and 3,

The test results showed that the cast iron treated with the proposed modifying mixture has higher mechanical properties. The tensile strength of the pig iron treated with the proposed mixture is 9.5 kg / mm higher compared with the iron treated with the known mixture, and its hardness is 25 HB,

Claims (1)

When using the invention, the quality of castings is improved by increasing the mechanical properties of cast iron (strength of 9.5 kg / mm), hardness - by 25 HB, than that of the prototype); increase the service life of parts made of cast iron, modified by the proposed mixture; reducing the consumption of expensive, deficient and toxic bismuth, as well as aluminum and boron. In addition, there is a 35 improvement in the working conditions of the staff by reducing the consumption of toxic bismuth; the time of heat treatment is reduced from 34 to 19 hours, and the cost of 1 ton of suitable casting is reduced by 2.6 rubles due to a decrease in the heat treatment cycle. Invention Modifying mixture for malleable containing aluminum, boron and bismuth, characterized in that, in order to improve the mechanical properties and reduce the duration of heat treatment of cast iron, it additionally contains copper scale in the following ratio, wt.%: Aluminum4.7 - 5.7 Bor0.5 - 0.55 Bismuth 0.7-0.75 Medna okapina93,0 - 94,1 thirty 40 50 55 note 1-3 - a mixture of the proposed modifier; 4-5 - mixtures having a content of aluminum, boron, bismuth and copper oxide above and below the proposed one; 6 - the modifying mixture is known. table 2 The duration of the heat treatment of cast irons modified by the known and proposed compositions MO MO diffi to auto p s Table 1 713202548 Table 3 The mechanical properties and structures of the samples after annealing according to the regimes are respectively tab. 2 Soe-Mechanical Properties Structure Limit Relative-Strength Durability. udpine- HB kg / mm ing,% 144.5 8,0146Гф 9, immediately 15-40, П 2 П25 Fe 75 242.0 9,0131Гф 9, Hraz 15-40, P 2 P10 Fe 90Ts2 345.5 6,0163Гф 9, Граз 25-45, ПБО Fe 40 4 30.5 5.9116Гф 6.7.8, Graz 45-90, Fe 533.0 9, B, Graz 25-60, P6 Fe 94 635.0 10.0 121Gf 8, Graz 5-100, Fe Compiled by N.Shepitko Editor M.KelemeshTehred A.KravchukKorrektor S.Shekmar Order 2614/24 Circulation 604 Subscription VNIIPI USSR State Committee On affairs of inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, st. Project, 4